Ring seals are typically annularly shaped, defining an axially aligned hole for gas or fluid passage, two axially opposed end surfaces, a radial inner surface and a radial outer surface. A simplistic ring seal has planar end surfaces and smooth circular radial inner and outer surfaces that define the inner diameter (ID) and outer diameter (OD) of the ring seal. However, it is common practice in the industry to utilize seals having different radial cross-sections to obtain varying sealing capabilities for different fluid flow environments.
A commonly used ring seal is circular and has a radial cross-section of a “C” shape. These “C seals” are constructed with the open side of the C construction facing the center of the ring such as is described in U.S. Pat. No. 5,354,072, (“the '072 patent”) or with the open side of the C facing away from the center of two mating surfaces are brought together with the C seal in the middle, where the C seal is compressed with the open side of the C cross-section closing during compression. The ductile properties of the seal permit plastic deformation to occur without damaging the mating surfaces.
Additional seals that have been available include “V” seals, which are also circular, but instead of having a “C” cross-section, have a “V” cross-section with the low point of the V constructed to point either inwardly or outwardly towards the center of the seal. Other seals known in the art include “Z” seals and simple O-rings. These other types of seals are discussed, for example, in U.S. Pat. No. 6,708,985 (“the '985 patent”). Both of the '072 and '985 patents are herein expressly incorporated by reference, in their entirety. Still another type of ring seal known in the industry is the “W” seal. Such a sealing system is disclosed, for example, in U.S. Pat. No. 7,140,647 (“the '647 patent”), also herein expressly incorporated by reference, in its entirety. The “W” seal in the '647 patent uses a snap ring situated on the inside of a retaining ring, identified in the patent as a guide, to retain the W-seal in the retainer and to keep the sealing surfaces on the W-seal or gasket protected from scratches. The '647 patent retainer or guide also has a snap ring situated on its outside diameter to keep the retainer engaged in the ‘counterbore.’
FIGS. 1-4 illustrate a typical prior art W-seal 2, comprising a retainer sleeve 2a, and a metal seal 2b. As discussed above, the assembly 2 further comprises an interior snap ring 2c and an exterior snap ring 2d. To accommodate these snap rings, there is provided a first Outside Diameter (OD) groove 2e on the outer surface of the retainer sleeve 2a, and an Inside Diameter (ID) groove 2f on the inner surface of the retainer sleeve 2a. Additionally, a second OD groove 2g is provided on the outer surface of the metal seal 2b, which corresponds to the ID groove 2f, wherein the second OD groove 2g and the ID groove 2f together accommodate the interior snap ring 2c. It should be noted that the cut in the ring and seal shown in FIG. 2 is illustrative only, for the purpose of illustrating particular constructional features of the seal assembly. In actuality, both the seal and the retaining ring are circumferentially continuous and unbroken.
Thus, each prior art W-seal requires four separate parts, including two snap rings and three formed grooves for accommodating those snap rings, resulting in manufacturing complexity and relatively high cost. Additionally, these snap rings have been found to make it substantially more difficult to remove the seal from the counterbore when desired, causing productivity problems and sometimes damage to the seal assembly. For instance, when the seals are used to connect two channels designed to carry very high purity gases such as in a silicon deposition environment, impurities introduced into the system by the seal can impact the performance of an entire system. For example, out-gassing of impurities from the surfaces exposed to the interior of the vacuum environment in the system can unacceptably pollute the system. Because known W-seals are made to have a tight slip fit between the seal 2b and the retainer sleeve 2a and between the retainer sleeve 2a and the counterbore, minor damage to the counterbore material and the retainer sleeve during installation and removal during maintenance can increase the amount of material exposed to the vacuum environment, thereby increasing the potential for introduction of excess impurities from out-gassing from that material.
In one operation environment, gas and vapor handling equipment deliver reactant and inert gasses and vapors to a tool such as an epitaxial reactor, a plasma etcher, and the like, which are used in the manufacture of semiconductors. Such equipment includes gas sticks, which employ a semi-modular design and may be rapidly constructed and easily and quickly maintained. Maintenance would include replacement of active gas delivery and metering components along a gas flow path. Such active components may include valves, pressure regulators, mass flow meters and mass flow controllers. The active components are secured in a gas flow path through a substrate or substrate blocks by the use of block or face type connectors.
The block connectors minimize contamination of the gas flow path by reducing the wetted surface. The wetted surface is the interior surface of a gas flow path that contacts the gas. The smaller the wetted surface that is presented the smaller the amount or likelihood that the surface will be contaminated with unwanted gas species during assembly during an initial build or during maintenance when the flow path is torn down.
Some prior seals and retainers for face block systems may introduce unwanted contaminants via abrasion and physisorption and chemisorption on the seal surfaces. The existing face seal systems use a small area, sealing zone to reduce contamination by reducing the wetted area at the connector joint. This is done by making sure the sealing zone is essentially flat with no portions of one connector extending into the other connector as is common in less stringent applications. The threaded members holding the connector halves are positioned a substantial distance away from the flow path to avoid contaminating it with particulates generated during tightening or loosening of the connector bolts. Likewise there is no threading along the outside of the flow path at the connector break of the type found in a garden hose. Such a “threaded pipe” construction might generate particulates in the immediate vicinity of the flow path during tightening. Despite this some problems remain. The W-seal is an example.
The above described seal uses a retainer that cannot be characterized as “low force.” The snap ring on the outer surface or its retainer comes in sliding contact with the wall of the counterbore during assembly. Because a relatively large force is needed to set the seal and retainer, alignment problems can arise and the snap rings abrade the counterbore walls generating contaminating particulates.
What is needed, for certain sealing system applications, is a seal system that affords certain functional advantages without the necessity and expense involved in employing snap rings, and which is preferably constructed to permit easy removal from the counterbore.